Ensures that null data passed to an input filter is cast to an empt…

…y array

Per #159, `BaseInputFilter` works inconsistently when a `null` value is
passed to `setData()`, interpreting this as an invalid argument type
versus an empty data set. This is particularly problematic with nested
sets sent via an API, as they may be nullable. In such cases, they
should be treated the same as if an empty array were provided.

src/BaseInputFilter.php

@@ -172,15 +172,21 @@ public function remove($name)
     /**
      * Set data to use when validating and filtering
      *
-     * @param  array|Traversable $data
+     * @param  null|array|Traversable $data null is cast to an empty array.
      * @throws Exception\InvalidArgumentException
      * @return InputFilterInterface
      */
     public function setData($data)
     {
+        // A null value indicates an empty set
+        if (null === $data) {
+            $data = [];
+        }
+
         if ($data instanceof Traversable) {
             $data = ArrayUtils::iteratorToArray($data);
         }
+
         if (! is_array($data)) {
             throw new Exception\InvalidArgumentException(sprintf(
                 '%s expects an array or Traversable argument; received %s',

test/InputFilterTest.php

@@ -78,4 +78,30 @@ protected function createFactoryMock()
 
         return $factory;
     }
+
+    /**
+     * Particularly in APIs, a null value may be passed for a set of data
+     * rather than an object or array. This ensures that doing so will
+     * work consistently with passing an empty array.
+     *
+     * @see https://github.com/zendframework/zend-inputfilter/issues/159
+     */
+    public function testNestedInputFilterShouldAllowNullValueForData()
+    {
+        $filter1 = new InputFilter();
+        $filter1->add([
+            'type' => InputFilter::class,
+            'nestedField1' => [
+                'required' => false
+            ]
+        ], 'nested');
+
+        // Empty set of data
+        $filter1->setData([]);
+        self::assertNull($filter1->getValues()['nested']['nestedField1']);
+
+        // null provided for nested filter
+        $filter1->setData(['nested' => null]);
+        self::assertNull($filter1->getValues()['nested']['nestedField1']);
+    }
 }